Heat exchangers, such as ones used in heating, ventilation, and air conditioning (HVAC) systems, and other similar devices (generally called heat exchangers) control or alter thermal properties of one or more fluids, such as air. In some cases, tubes (also called heat exchange tubes or HX tubes) disposed within these devices are used to transfer through the HX tubes a working fluid that is at a different thermal condition from that of fluid outside the HX tubes, thereby altering the thermal properties of the working fluid within the HX tubes and the fluid, such as air, passing over the outside of the HX tubes. The temperature of the working fluid and the fluid passing over the outside of the HX tubes can increase or decrease, depending on how the device is configured. The working fluid and the fluid outside the HX tubes do not mix at any part of the heat exchanger. There have been many approaches to increase the thermal efficiency of the HX tube that in turn may increase the efficiency of the device, since the overall thermal efficiency of the device depends on both the working fluid and fluid outside the HX tubes.
One approach to increase thermal efficiency of the HX tube is to enhance the turbulence of working fluid inside the HX tube by adding baffles or turbulators inside the HX tube. In another approach, the HX tube has multiple dimple like deformations on the HX tube surface to increase velocity of the working fluid at the deformations, thus increasing the turbulence.
All the above approaches are aimed at enhancing the thermal efficiency of the HX tubes alone, but not the overall thermal efficiency of the heat exchanger which also depends on the interaction between the HX tubes and outside fluid. In addition to the overall thermal efficiency of the heat exchanger device, any improvement in the pressure drop of the outside fluid can generate considerable energy and cost savings.